EHD friction properties of ISO VG 320 gear oils with smooth and rough surfaces

Balasubramaniam VENGUDUSAMY; Claus ENEKES; Reiner SPALLEK

doi:10.1007/s40544-019-0267-5

Friction 2020, 8(1): 164-181 https://doi.org/10.1007/s40544-019-0267-5

Research Article |

Open Access | Issue | Published: 19 March 2019

EHD friction properties of ISO VG 320 gear oils with smooth and rough surfaces

Show Author's Information Hide Author's Information Balasubramaniam VENGUDUSAMY(

), Claus ENEKES, Reiner SPALLEK

Klüber Lubrication München SE & Co. KG, Geisenhausenerstraße 7, Munich 81379, Germany

Keywords:

friction, film thickness, ISO VG 320 gear oil, roughness effect, EHD, micro-EHD

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VENGUDUSAMY B, ENEKES C, SPALLEK R. EHD friction properties of ISO VG 320 gear oils with smooth and rough surfaces. Friction, 2020, 8(1): 164-181. https://doi.org/10.1007/s40544-019-0267-5

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Abstract

The elastohydrodynamic (EHD) friction properties of seven ISO VG 320 gear oils including three polyalphaolefins (PAOs), three polyglycols (PG) and a mineral oil have been investigated in rolling/sliding conditions at six different temperatures and three roughnesses. Film thickness, Stribeck and traction curves have been generated using a ball-on-disc tribometer. Film thickness results are in agreement with previous work that it is primarily controlled by pressure-viscosity coefficient and viscosity of lubricants. The results with smooth surface show that all oils experience significant shear heating leading to friction reduction at higher strain rates or lambda ratios but only PGs reach limiting friction whereas mineral oil and PAOs do not. Friction curves obtained at different temperatures and roughnesses enable simulating an extensive range of lubrication regimes and allow isothermal friction correction for shear heating. Stribeck curves with rough surfaces show an increase in friction in the lambda range of 0.5–3.5, where asperity separation varies from partial to full–indicating that roughness effects can be expected even under full film condition. This increase in friction is attributed to formation of a micro-EHD region, and is seen only with mineral oil and PAOs whereas not with PGs. The results also highlight how EHD friction properties of different family of fluids could be influenced by roughness effects, and the possible mechanisms are discussed.

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About this article

EHD friction properties of ISO VG 320 gear oils with smooth and rough surfaces

Show Author's information Hide Author's Information Balasubramaniam VENGUDUSAMY(

), Claus ENEKES, Reiner SPALLEK

Klüber Lubrication München SE & Co. KG, Geisenhausenerstraße 7, Munich 81379, Germany

Abstract

Keywords: friction, film thickness, ISO VG 320 gear oil, roughness effect, EHD, micro-EHD

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Acknowledgements

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Publication history

Received: 20 April 2018

Revised: 22 October 2018

Accepted: 23 December 2018

Published: 19 March 2019

Issue date: February 2020

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Acknowledgements

The authors wish to thank Mr. Christoph Sedlak for conducting the tribological tests and Dr. Michael Hochmann, Mr. Matthias Pfadt, Mr. Thomas Jorgensen and Dr. Jochen Mühlemeier for organising and performing lubricant analysis. The authors would also like to thank Prof. Hugh Spikes, Imperial College London for discussions and valuable suggestions.

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